Climate Reading: The Polar Vortex Rebuilds for Fall

Arab Weather - Meteorologists at the Arab Weather Regional Center said that the countries of the Northern Hemisphere will enter the climatic fall season in a few days, i.e. at the beginning of next September. September 1st is considered the beginning of autumn according to meteorology, and with its beginning, weather systems begin to gradually change, as summer systems recede while the Arctic vortex begins to build, heralding the arrival of autumn and preparing for winter.

Summer systems begin to collapse with the beginning of fall.

Starting with the beginning of autumn, summer weather systems begin to retreat from polar and subpolar regions. The apparent movement of the sun begins to decline southward, with nights lengthening. The tropical highs that dominated during the summer gradually withdraw, and the centers of thermal depressions, such as the seasonal depression in the Arabian Peninsula, fill up.

At the same time, the Southern Hemisphere is beginning to enter spring, with temperatures gradually rising after winter, paving the way for warmer, more moderate weather than the one that has prevailed over the past few months.

Westerlies are becoming active.

As autumn approaches, the Arctic vortex begins to form and consolidate again due to increased cooling as the axis of solar radiation in the Arctic begins to tilt.

Weather maps indicate that the westerly zonal winds are expected to begin activity at the end of this month, gradually increasing in strength during September and October. These winds move from west to east in the upper layers of the atmosphere, especially at an altitude of approximately 10 hectopascals (about 30 km), and are often focused on the 60°N latitude, as it represents approximately the boundary of the polar vortex.

When the winds are strong and positive (heading in the normal westerly direction), the polar vortex is strong and stable.

When it weakens or shifts eastward (negative values), this indicates a weakening or collapse of the vortex, and this is often associated with cold air rushing towards the middle latitudes (such as Europe or the Middle East).

Characteristics of autumn in Arab countries

Autumn is a transitional season, marked by increased weather fluctuations and the deepening penetration of cold air masses from north to south, generating atmospheric instability and the onset of the rainy season in many Arab countries. Temperatures also begin to gradually decline, and thermal fluctuations increase during two closely spaced periods due to the conflict between air masses with different characteristics.

On the other hand, respiratory diseases increase during this season due to the significant changes in temperature.

For those interested and specialists: What is the polar vortex?

The polar vortex is a circular low-pressure system that forms over the Earth's North and South Poles. It consists of a massive mass of cold air surrounding the pole and is trapped by the Earth's rotation and the Coriolis effect. This vortex creates an integrated weather system that is significantly influenced by temperature and seasonal changes.

The polar vortex is formed by the interaction between cold air accumulating above the poles and the air movement around them. During winter, the polar vortex expands due to lower temperatures, strengthening the low-pressure system. This expansion can cause cold air masses to flow into more temperate regions in the Northern Hemisphere, resulting in severe cold spells.

During winter, temperatures in polar regions drop, strengthening and expanding the polar vortex. This expansion can lead to cold air masses flowing farther south, causing severe cold waves and snowstorms in temperate regions. In summer, the polar vortex shrinks due to rising temperatures, but it begins to rebuild as fall approaches in preparation for the next winter.

And God knows best.